Tap water always contains a certain amount of water hardness salts such as calcium carbonate which eventually deposit on surfaces which are often in contact with said water, resulting in an unaesthetic aspect of said surfaces. This limescale deposition phenomenon is even more acute in places where water is particularly hard.
Typically, these limescale deposits are removed by using a cleaning composition comprising an acid which "dissolves" limescale, typically phosphoric acid. however, phosphoric acid has become subject to discussions, in relation to environmental questions. It is therefore an object of this invention to find an alternative to phosphoric acid in this particular context.
In addition, it has been observed that state of the art compositions do not perform equally well on all limescale-containing stains, particularly on limescale-containing stains which are mainly found in the bathroom. These bathroom-type stains appear to contain not only calcium carbonate, but also soap scum, and it has now been found that soap scum is detrimental to the limescale removing performance of said compositions.
It is therefore an object of the present invention to obviate this issue in providing a cleaning composition for the removal of limescale, said composition possessing a superior limescale removing capacity, said composition being also effective on limescale-containing bathroom-type stains.
DE 33 40 033 describes a composition for the removal of limestone traces on laundry; these compositions contain maleic acid and nonionic surfactants, as well as high amounts of phosphoric acid and urea.
EP 200 776 describes a method to remove precipitates containing mainly calcium carbonate by using a mixture of a Lewis acid and a protonic acid, possibly maleic acid.
J 61 28 3700 (abstract) discloses detergent compositions for bathroom which comprises a maleic acid or anhydride-based polymer and a nonionic surfactant; these compositions also comprise cationic surfactants.
EP 0 336 878 discloses an acidic cleaning composition comprising conventional surfactants and a dicarboxylic acid. Maleic acid is not mentioned.